Hydrogen is a relatively environmentally-friendly, abundant fuel source that, when reacted with oxygen, produces energy and water Hydrogen has been traditionally used as fuel for rockets, but has also been used as fuel for automobiles. In such cases, noncombustive technologies such as fuel cells have been used to extract energy from hydrogen. In particular, the fuel cells have been designed to host a reverse electrolysis process to generate electricity and water. Recently, fuel cells have been employed as replacements for batteries in portable, hand-held devices.
Although hydrogen fuel sources have many technical advantages over other fuel sources, storing hydrogen has presented a challenge. For example, in some cases, hydrogen is stored as a compressed gas in a storage tank, but such tanks may only be capable of holding up to about 10% of hydrogen by weight. In other cases, hydrogen is extracted from liquid hydrocarbons with CO (carbon monoxide) as an undesirable byproduct. Moreover, hydrogen gas is a relatively flammable material, and safety may become an issue if a storage container in which the hydrogen is stored becomes damaged.
Recently, other storage options, such as solid state hydrogen storage, have been investigated. For example, metal hydrides have been discovered as viable solid state hydrogen storage materials. However, metal hydrides typically absorb atomic hydrogen by forming covalent sigma bonds, and as a result, the hydrogen may be relatively difficult to remove. For example, high temperatures (e.g., >600° C.) may be used to release the hydrogen. Other hydrides, such as aluminum hydrides with alkali metals such as sodium, potassium, and lithium, may desorb hydrogen at practical temperatures and pressures for mobile consumer applications (e.g., at temperatures below about 200° C. and at pressures about 1 atm), but have low weight percentage of hydrogen adsorption. Still other hydrides may produce effective hydrogen storage materials capable of storing about 7% hydrogen by weight at practical temperatures and pressures; however, when these materials are subjected to a temperature in a range of between about 50-150° C., they may only release about 5% hydrogen by weight. Alternatively, a relatively large amount of pressure may be needed to cause a release from the material of more than 5% hydrogen by weight.
Accordingly, it is desirable to have a hydrogen storage material that can remain stable at room temperature (e.g., between about 20-25° C.) and at pressures of about 1 atm. It is also desirable for the hydrogen storage material to adsorb and desorb hydrogen at temperatures that are below about 200° C. and at pressures less than about 1 atm. Moreover, it is desirable for the hydrogen storage to be capable of releasing more than 6.5% hydrogen by weight at such temperatures and pressures. Furthermore, other desirable features and characteristics of the inventive subject matter will become apparent from the subsequent detailed description of the inventive subject matter and the appended claims, taken in conjunction with the accompanying drawings and this background of the inventive subject matter.